The invention relates to a device for a correctly targeted formation of a drill hole centrally in the femoral attachment site of the posterior cruciate ligament of a knee joint, said device comprising a hollow shaft through which a drill wire can be guided.
Devices of this kind, called femoral sighting devices, for introducing a drill wire into a femur are marketed by the Applicant.
A femoral sighting device is illustrated in the book entitled “Arthroskopische Chirurgie” [Arthroscopic Surgery] by Doctor Michael Strobel, Arthroskopische Chirurgie, Springer Verlag Berlin Heidelberg 1998, chapter 2, page 513, FIGS. 2.15-8.a. 
This device is more or less in the shape of a screw driver. The device comprises a hollow shaft. At its proximal end, the hollow shaft is received in a handgrip.
The hollow shaft extends through the handgrip along the longitudinal axis of the handgrip. A drill wire can be guided through the hollow shaft.
Devices of this kind are used in the field of reconstruction of the posterior cruciate ligament of the knee joint.
Lying in the center of the human knee there are two intersecting ligaments that extend from the tibia to the femur, namely the anterior cruciate ligament and posterior cruciate ligament. These two ligaments, together with the menisci, the collateral ligaments and muscles, ensure the necessary stability of the knee joint and as a consequence are of very great importance.
If the posterior cruciate ligament is torn, the damaged knee joint has to be restabilized by surgery. For this purpose, the torn posterior cruciate ligament is replaced by another tendon. Suitable tendons for this reconstruction of the cruciate ligament are the tendon of a muscle on the rear aspect of the thigh, the so-called semitendinosus muscle, or the patellar tendon.
In both cases, the tendon is guided through bone tunnels in the tibia and femur and positioned at the location where the intact posterior cruciate ligament is normally situated.
One anatomical feature here is that the approximately circular femoral attachment of the posterior cruciate ligament has an outer margin which partly runs along the cartilage-bone interface of the femur. For reconstruction of the posterior cruciate ligament, the distal end of the shaft of the sighting device is placed approximately centrally on the femoral attachment of the posterior cruciate ligament. The precision of this placement and also its orientation depend on the dexterity of the operating surgeon.
A drill wire is then passed through the hollow shaft and inserted as centrally as possible into this femoral attachment. This drill wire is subsequently pushed through the femur in an intra-articular to extra-articular direction. A hollow drill is engaged over the drill wire that has been positioned in this way, and a drill channel is in this way formed in the femur.
The drill channel is made in such a way that it has two sections. Seen in the intra-articular to extra-articular direction, the diameter of the first section is greater than that of the second section. The cruciate ligament replacement is then guided usually as a double loop into the first section of the drill channel. A securing thread is drawn through the bow of this double loop. This securing thread extends through the second section of the drill channel. At the medial outer end of the drill channel, the securing thread is fixed with a fixing stud.
The free ends of the cruciate ligament replacement are finally guided through a tibial drill channel and, for example, fixed with a bone dowel.
In all cruciate ligament reconstructions, the placement of the drill channels is a critical step in the operation.
The position and course of the femoral drill channel determine whether the reconstructed posterior cruciate ligament is anchored on the femur in the same way as anatomically in the natural posterior cruciate ligament and whether it protrudes from the femur in the same way anatomically as in the natural posterior cruciate ligament. In this respect, the formation of a drill hole will be described as correctly targeted if the drill channel formed is located with such precision that the replacement cruciate ligament protrudes from the femur in anatomically the same way as the natural posterior cruciate ligament.
It is therefore imperative to ensure that the guide wire passes centrally and in a correctly targeted manner through the femoral attachment of the posterior cruciate ligament. Even slight deviations can lead to subsequent instability in the patient's knee joint.
In practical application, it has now been found that, as a result of anatomical circumstances or because of hands-free insertion of the drill wire, the position of the drill channel can deviate from the natural position of the femoral attachment of the posterior cruciate ligament. This leads to noticeable instability in the knee joint on which surgery has been performed.
It is therefore an object of the present invention to remedy this situation and to configure a device in such a way that it makes correctly targeted and correctly positioned formation of a drill hole easier.